High power laser imaging is increasingly employed in modern printing operations. One example of a laser imaging technique utilized in these operations is offset lithography. In a typical lithographic process, a printing plate (e.g., a flat plate, an outer surface of a cylinder, belt) can be configured with “image regions” formed of, for example, hydrophobic and oleophilic material, and “non-image regions” formed of a hydrophilic material. Such image regions correspond to areas on a print media that are occupied by a printing or a marking material such as ink, whereas the non-image regions correspond to the areas on the print media not occupied by the marking material.
Variable data lithography (also referred to as digital lithography or digital offset) utilized in printing processes typically begins with a fountain solution that dampens an imaging plate (e.g., silicone) on an imaging member (e.g., drum, cylinder, belt). The fountain solution forms a film on the imaging plate that may be about one (1) micron thick. The imaging member rotates to an “exposure” station where a high power laser imaging module (LIM) removes the fountain solution at the locations of the imaging plate where the image pixels are to be formed. This forms a fountain solution based ‘latent image’. The drum then further rotates to a ‘development’ station where lithographic-like ink may be brought into contact with the fountain solution based ‘latent image’ and ink ‘develops’ onto the places where the laser has removed the fountain solution. The drum then rotates to a transfer station where the ink is transferred to a print media such as paper.
A LIM that forms the latent image may include one or more lasers that work with one or more optical components to direct the laser onto the printing plate. Each LIM can utilize a linear output high power infrared (IR) laser to illuminate a digital light projector (DLP) multi-mirror array, also referred to as the “DMD” (Digital Micromirror Device). The laser provides constant illumination to the mirror array. The mirror array deflects individual mirrors to form the pixels on the image plane to pixel-wise evaporate the fountain solution on the silicone plate. If a pixel is not to be turned on, the mirrors for that pixel deflect such that the laser illumination for that pixel does not hit the silicone surface, but goes into a chilled light dump heat sink.
During operation, the LIM optical components can generate a large amount of heat due to the amount of power used by the lasers within the LIM. This heat can negatively affect the optical components. For example, large amounts of heat can cause the optical components of the DMD to operate improperly, operate with a reduced life expectancy, or in extreme instances, cause the optical components to completely fail. During operation, a maximum temperature allowed at the DMD micromirror surface is about 70° C. for reliable operation. When the micromirrors are in the “on state” printing mode, the temperature of the mirrors may increase to over 90° C. When the mirrors are in an “Off-State” more energy is absorbed at the substrate. As a result, the temperature of the micromirrors may increase to temperatures above 130° C., which is at least 50° C. above the 70° C. threshold for reliable operation. Currently used methods may be inefficient in cooling the optical components to a proper temperature range.